Implantable prosthesis with direct mechanical stimulation of the inner ear

ABSTRACT

A prosthesis for stimulation of the inner ear, comprising means for excitation which generate vibrations which can excite the ear of a patient, and an implantable part comprising a rod which can transmit vibrations and which is configured in such a way that it can directly transmit vibrations generated by the means of excitation to the inner ear of a patient.

FIELD

The present disclosure relates to ear stimulation prostheses forrehabilitation of patients with disorders of the inner ear.

BACKGROUND

The inner ear is a sensory organ of which the function is to transcribevibration waves between 0 and 20 kHz from the environment into a sensoryinflow. It includes two physically distinct portions having twodifferent respective functions, namely the balance portion and thehearing portion.

The balance portion, called the vestibule, has the function of encodingvibration waves between 0 and 800 Hz. It also makes it possible tosituate the direction of the head with respect to its environment, byacceleration measurement systems in the semicircular canals. The hearingportion, called the cochlea, encodes the vibration waves between 20 Hzand 20 kHz.

The pathologies that may affect the inner ear can primarily beclassified into three categories, namely loss of auditory acuity,balance disorders and tinnitus.

The main cause of these pathologies is associated with the natural agingof the sensory cells, resulting in hearing disorders (presbycusis,age-related deafness) and balance disorders (vestibulopathy, age-relatedhypoflexia).

Some diseases, such as Meniere's disease, can trigger all three types ofpathologies (deafness, tinnitus and vertigo).

There are a number of possibilities for treatment of these pathologies.For some cases of deafness associated with transmission and vestibulardisorders, there are surgical treatments, such as the opening ofendolymphatic sacs or vestibular nerve section or middle ear surgeries.These treatments have the disadvantage of being irreversible.

Some drugs or rehabilitation treatments can attenuate vertigo, tinnitusand sudden or fluctuating deafness. These treatments do not cure thedisease, but simply enable the affects thereof to be reduced. Thesepathologies can also be treated with an apparatus. However, there iscurrently no apparatus enabling all of these pathologies to be treated.

For deafness, hearing aids are designed to amplify the acoustic waves.They are commonly used to treat all levels of deafness, from slight toprofound. There are also systems implanted into the middle ear, whichare designed to mechanically amplify the movements of the ear ossicles(U.S. Pat. Nos. 5,913,815 and 6,293,903). There are systems for boneconduction, by means of a vibrator integrated in a pair of eyeglasses,for example, which are designed to cause the skull to vibrate so as totransmit the vibration wave to the inner ear. These latter systems arelimited to the treatment of deafness associated with a transmissionproblem, because the pressure exerted on the skin to transmit thevibration to the skull must be limited. There are also implanted boneconduction systems in which the vibrator is either implanted or can beconnected by an opening in the skin to an implant attached to the skull(U.S. Pat. No. 4,498,461, WO 02/09622). Electric stimulators (intra- orextra-cochlear implants), directly stimulating the auditory nerve, areused in cases of significant deafness, i.e. when the acoustic waves areinsufficient for stimulating the auditory nerve.

There is no apparatus for vertigo. For tinnitus, a masking system hasbeen proposed, which sends a noise to the inner ear to mask the tinnitus(U.S. Pat. No. 5,325,872). In addition, external hearing aids make itpossible to correct tinnitus associated with deafness: the correction ofthe deafness leads to a reduction in the tinnitus. Electric stimulatorsof the inner ear are also used to reduce tinnitus, when the deafness istoo severe to be treated acoustically.

Hearing aids and masks have the advantages of not requiring surgery andof being reversible and compatible with MRI. However, they are generallyrelatively visible, and therefore unaesthetic. In addition, theysometimes have contraindications (aplasia of the outer ear, externalotitis, eczema, and so on). They often cause acoustic feedback due totheir structure and in particular the closeness of the microphone to theearphone. Some of these apparatuses require plugging the auditory canal,which raises the problem of amplification of low-frequency sounds, andis often disturbing for the patient who then hears more body sounds(chewing, blood circulation). Moreover, these apparatuses operate onlyon a frequency band between 125 and 6000 Hz due to the use of anearphone.

Systems implanted in the middle ear, on the other hand, are discreet anddo not require blocking of the auditory canal. They cause littleacoustic feedback, thereby allowing for more high-frequency sounds thanwith hearing aids. They cause less distortion and operate in a widerfrequency band (up to 10 kHz) because they do not use an earphone.However, they require surgery of the middle ear and general anesthesia,with all of the risks of these operations (facial nerve, ear ossicles),which makes them relatively irreversible and incompatible with MRI andradiotherapy, and raises problems in the event of a breakdown or failureof the apparatus. By comparison with hearing aids, these apparatuses arerelatively expensive, and if the deafness changes, their capacity foradjustment is limited due to the use of an electromagnetic transducer.Moreover, their bandwidth does not cover the entire spectrum to whichthe inner ear is normally sensitive (limited to frequencies between 125Hz and 10 kHz).

Non-implanted or semi-implanted bone conduction systems have theadvantage of providing quality sound. They do not require the auditorycanal to be plugged either, and do not generate acoustic feedback.However, they are highly visible and therefore unaesthetic, and consumea large amount of power. Moreover, they provide little or no left/rightselectivity due to the mode of transmission used (through a skull bone).Non-implanted systems must clamp the skin (conduction of vibrationsthrough the skin), which is uncomfortable for the patient, and evenpainful, and can cause necrosis of the skin. Semi-implanted systemsrequiring a permanent opening in the skin barrier lead to risks ofinfection.

Cochlear implants require complex surgery, therefore with risks, whichis irreversible, presenting a problem in the event of failure of thetreatment or breakdown of the apparatus. They are incompatible withimaging systems, expensive, and their bandwidth is limited tofrequencies between 125 and 6000 Hz.

SUMMARY

This invention is intended to overcome these disadvantages. Thisobjective is achieved by providing an inner ear stimulation prosthesisincluding excitation means designed to cause vibrations capable ofexciting the ear of a patient.

According to the invention, this prosthesis comprises an implantableportion, including a rod capable of transmitting vibrations and that isdesigned so as to be capable of transmitting the vibrations generated bythe excitation means directly to the patient's inner ear.

The rod is advantageously designed to be placed in contact with asemicircular canal of the patient's inner ear, preferably the externalsemicircular canal of the patient's inner ear.

According to a special feature of the invention, the rod is made of ahard and rigid biocompatible material chosen from metals, plasticmaterials, and ceramic materials.

The rod advantageously has a cross-section with a flattened shape.

According to a special feature of the invention, the rod comprises atleast one elbow so as to be capable of connecting an external portion ofthe patient's skull with the inner ear without requiring complex surgeryinvolving total anesthesia of the patient.

The rod preferably has a length between the elbow and its end in contactwith a portion of the patient's inner ear of between 20 and 30 mm andhas an elbow angle between its two end portions of between 70° and 130°.

The surface of the implantable portion is also preferably treated so asto prevent any osseointegration.

The rod is preferably pivotably mounted on a support.

According to a special feature of the invention, the excitation meansare arranged in an external casing and are designed to generatevibrations intended to be transmitted through the patient's skin to aplate rigidly connected to the rid.

The plate preferably has a substantially rectangular shape with foamedges of which the length is between 6 mm and 20 mm and the width isbetween 3 mm and 10 mm.

According to a special feature of the invention, the external casing isintegrated in an object capable of being held on the patient's head sothat the excitation means are arranged opposite the plate of theimplantable portion.

The object capable of being held on the patient's head is preferablyselected from either a pair of eyeglasses or a casing that fits aroundthe ear.

According to a preferred embodiment of the invention, the externalcasing includes at least one magnetic part intended to cooperate with atleast one magnetic part provided in the implantable portion in order tohold the excitation means opposite the plate.

According to a preferred embodiment of the invention, the excitationmeans are integrated in the implantable portion and coupled directlywith the rod.

According to a preferred embodiment of the invention, the rod is rigidlyconnected to attachment means for attaching the rod to the patient'sskull bone.

The excitation means are preferably housed in an external casingequipped with coupling means, so as to be removable attached through thepatient's skin to attachment means intended to be attached to thepatient's skull bone.

According to a preferred embodiment of the invention, the externalcasing containing a microphone is intended to be attached on the side ofa totally defective ear of the patient, while the rod is intended to beattached so as to excite the other non-defective ear of the patient,with the vibrations generated by the excitation means being transmittedto the rod by bone conduction of the patient's skull bone.

The invention also relates to a hearing aid, and/or a prosthesis forneurostimulation against tinnitus and/or balance disorders, having atleast one of the features disclosed above.

The invention also relates to an implantable prosthesis portion,consistent with one of the features disclosed above.

Because it does not involve the ear ossicles or the middle ear, theprosthesis according to the invention can be implanted by a simplesurgical procedure requiring only local anesthesia. Such surgerytherefore has few of the risks of surgical complications, and isreversible.

Because a vibration is transmitted directly to the inner ear, theprosthesis according to the invention makes it possible to transmit theentire frequency band (0 to 20 kHz) to which the inner ear is normallysensitive. The prosthesis according to the invention can therefore beused as an auditory prosthesis, and/or as a neurostimulation prosthesisfor fighting tinnitus and/or balance disorders.

In the case of hearing correction, it provides the possibility ofsignificant amplification without the risk of generating acousticfeedback. It therefore makes it possible to correct all disorders of theear (deafness, tinnitus, balance). Because the inner ear is directlystimulated, the left/right selectivity is very good, which allows forselective and appropriate correction of the two ears independently ofone another. Moreover, the prosthesis according to the invention doesnot require even partial plugging of the external auditory canal.

DRAWINGS

A preferred embodiment of the invention will be described below, by wayof a non-limiting example, in reference to the appended drawings, inwhich:

FIG. 1 diagrammatically shows an implantable prosthesis according to theinvention, installed on the patient's head;

FIGS. 2 and 3 respectively show, in greater detail, in perspective andin a side view, the implantable portion of the prosthesis shown in FIG.1;

FIG. 4 shows in greater detail, in a front view, the external portion ofthe prosthesis shown in FIG. 1;

FIG. 5 shows, in a front view, an alternative of the external portion ofthe prosthesis shown in FIG. 1;

FIG. 6 shows the way in which the external portion of the prosthesisshown in FIG. 5 is worn by the patient;

FIGS. 7 a and 7 b respectively show, in a partial profile and a frontview, an alternative of the implantable portion of the prosthesisaccording to the invention;

FIGS. 8 and 9 show, in a front view, alternatives of the externalportion of the prosthesis shown in FIGS. 7 a and 7 b;

FIG. 10 shows the way in which the implantable portion of the prosthesisshown in FIGS. 7 a, 7 b and 9 is attached to a patient's head;

FIGS. 11 and 12 respectively show, in front and profile views, theexternal portion of the prosthesis corresponding to the implantableportion shown in FIGS. 7 a, 7 b and 9;

FIGS. 13 and 14 show two other alternatives of the implantable portionof the prosthesis according to the invention;

FIG. 15 shows another entirely implantable alternative of the prosthesisaccording to the invention;

FIG. 16 shows the way in which the implantable portion of the prosthesisshown in FIG. 15 or 16 is attached to a patient's head;

FIGS. 17 and 18 respectively show, in front and profile views, theexternal portion of the prosthesis corresponding to the implantableportion shown in FIG. 13 or 14;

FIG. 19 shows another alternative of the implantable portion of theprosthesis according to the invention;

FIG. 20 shows the way in which the implantable portion of the prosthesisshown in FIG. 19 is attached to a patient's head;

FIGS. 21 and 22 show two alternatives of the external portion of theprosthesis corresponding to the implantable portion shown in FIG. 19;

FIG. 23 shows the implantable portion of an alternative of theprosthesis shown in FIGS. 19 and 20;

FIG. 24 shows another implantable portion intended to be associated withthe implantable portion shown in FIG. 22.

DETAILED DESCRIPTION

FIG. 1 shows an implantable prosthesis according to the invention. Inthis figure, the prosthesis includes an entirely passive implantableportion 1 designed to transmit vibrations to the inner ear, preferablyat the level of the semicircular canals, and an external portion 10integrating excitation means 11, such as a vibrator, intended tocooperate with the implantable portion 1. The external portion can alsocomprise signal processing means, one or more microphones, and/or otherelectronic and/or power elements.

In FIGS. 2 and 3, the implantable portion 1 includes a plate 3,preferably in the form of a reverse cup, connected to a rod 2. The plateis intended to be implanted under the skin in contact with the patient'sskull, preferably behind the ear (FIG. 1), so as to receive, through theskin, the excitation produced by the external portion 10. Theimplantable rod 1 advantageously forms at least one elbow 4 so that theangle between the plate 3 and the end of the rod 2 is between 70° and130°, so as to reach the inner ear through the antrostomy cavity fromthe external surface of the skull. Owing to the elbow 4, the implantablerod allows for acoustic piston-type transmission. The presence of anelbow also makes it possible to prevent a shock on the plate 3 fromcausing trauma due to pressure of the rod on the structures of the innerear.

The implantable portion 1 constituted by the plate 3 and the rod isadvantageously made in a single piece with foam edges, of a hard andrigid biocompatible material such as a biocompatible metal (for example,titanium, etc.), or a hard biocompatible plastic or ceramic material,which is selected so as to be a very good vibration transmitter, andpreferably compatible with MRI and radiotherapy.

The rod 2 advantageously has a cross-section with a flattened shape, forexample, rectangular with foam edges, around 3 mm wide and 1.5 mm thick.These dimensions make it possible to ensure good transmission ofvibrations between the plate and the inner ear, while reducing the risksof trauma to the skin. The length of the rod between the elbow 4 and itsdistal end intended to come into contact with the inner ear isadvantageously between 20 and 30 mm, and preferably between 24 and 26mm.

The distal portion of the rod 2 can have a non-flattened section so asto fit the body and concentrate the vibrations at the zone to bestimulated. The distal end of the rod 2 can advantageously have a shoefor facilitating its positioning and reducing the risk of trauma in theevent of a shock.

The plate 3 advantageously has a rectangular shape of which the lengthis between 6 and 20 mm and the width is between 3 and 10 mm, so as toprevent risks of trauma and even tearing of the skin, which may occur ifthe plate is too small or too large. These dimensions also allow forgood transmission of the vibrations generated by the vibrator 11 throughthe skin, which limits the pressure to be exerted on the skin betweenthe vibrator and the plate 3.

The end of the rod 2 is advantageously implanted so as to come intocontact with the semicircular canals of the inner ear, which have theadvantage of being very sensitive, preferably with the externalsemicircular canal, which is easily accessible by minor surgeryrequiring only local anesthesia.

More specifically, the rod is implanted using a tympanoplasty techniquewith retroauricular access followed by antrostomy and identification ofthe contact zone of the distal end of the rod 2. The rod 2 is thenapplied so that its distal end comes into contact with the shell of asemicircular canal, preferably the external semicircular canal, which iseasier to reach. When the rod is in place, its elbow 4 reaches theheight of the mastoid cortical bone, and the plate 3 is arranged in theretroauricular region away from the acoustic horn so as to preventacoustic feedback phenomena.

To fit the rod to the patient's body, it is possible to provide thesurgeon with a measuring tool such as a graduated rod or a malleablegauge for determining the length of the rod between the elbow and itsdistal end and the angle of the elbow. Next, it is possible to providethe surgeon with a set of rods having different lengths and possibleelbow angles so that he/she can choose the appropriate rod for thepatient's body. Alternatively, or in combination, it is possible toprovide tools for fitting the rod to the patient's body, and foradjusting the angle of the elbow and/or the length of the rod betweenits elbow and its distal end.

The implantable portion 1 preferably has a treated surface so as toprevent any osseointegration. The implantable portion 1 can also becovered with a coating of a relatively or entirely non-osseointegratablematerial, for example, silicone, PTFE or parylene.

In FIG. 4, the external portion includes excitation means 11 intended tobe applied to the skin opposite the plate 3, as shown in FIG. 1. Theexternal portion can also include a signal processor 13 powered by acell or a battery 12, and connected to the excitation means and possiblyto a microphone 14, and, if necessary, to one or more optionalmicrophones 15 intended, for example, to be arranged near the other earif it is entirely deaf.

In FIGS. 1 and 4, the external portion is advantageously integrated in atemple of the eyeglass frame, with the vibrator 11 being arranged in theend region of the eyeglass temple intended to be applied behind thepatient's ear, so as to be opposite the plate 3 of the implantableportion 1. By thus equipping the two temples of a pair of eyeglasses, itis possible to correct both ears of the patient, with the implantationof an implantable rod 1 in each ear. This provision makes it possible tocorrect problems of deafness and/or tinnitus and/or a balance disorder.

The external portion 10 can also be integrated in any other objectintended to be installed on the head, such as a headband or a headpiece,or a hair barrette. It can also be attached to the skull bytranscutaneous anchoring.

The prosthesis described in reference to FIGS. 1 to 4 also has theadvantages of being very discreet and of preserving the skin barrier.Owing to the use of a rod conducting the vibrations directly to theinner ear, the transmission of vibrations through the skin does notrequire the skin to be clamped in a manner that is uncomfortable for thepatient. Moreover, as the implantable portion is entirely passive, itdoes not present any risk of breakdown (by comparison with activeimplantable systems).

FIGS. 5 and 6 show an alternative of the external portion. In thisfigure, the external portion 10′ includes the vibrator 11, and possiblythe processor 13, the microphone 14 and the cell or battery 12, whichexternal portion is housed in a casing rigidly connected to theattachment means 15 that fit around the ear, enabling the vibrator 11 tobe held opposite the plate 3 of the implantable portion 1.

FIGS. 7 a, 7 b and 8 show alternatives of the implantable portioncomprising a rod 2 a rigidly connected to a plate 3 preferably pivotablymounted on a plate 7, 7′ thus comprising supports 6 extendingperpendicularly with respect to the plate 7, 7′ and supporting swivels 9positioned in cavities provided in the lateral sides of the plate 3 andforming a pivot pin. In FIGS. 7 a and 7 b, the plate 7 also supports twomagnetic parts 8 such as magnets, provided for the attachment of anexternal casing.

In FIG. 8, a magnetic part 8 such as a magnet is attached to the plate3, whereas no magnetic part is attached to plate 7′, so that the lattercan be smaller than the one shown in FIGS. 7 and 8.

It is also possible to consider mounting the magnetic parts 8 directlyonto the plate 3 or onto a positioning part 7″, for example in an arc ofcircle associated with the plate 3, as shown in FIG. 9. Then, the plate3 is not associated with a plate 7, 7′ on which it is pivotably mounted.

In FIG. 10, the implantable portion 1 a, 1 b is implanted under thepatient's skin, in the temporo-occipital zone, or substantially in themastoid region, so that the rod 2 a has a length between the plate 3 andthe elbow 4 that is greater than that shown in FIGS. 1 to 4.

In FIGS. 11 and 12, the external portion 10 a of the prosthesis,corresponding to the implantable portion 1 a shown in FIGS. 7 and 8includes a support plate 20 supporting two magnetic parts 18 intended tocooperate with the magnetic parts 8 of the implantable portion 1 a, anda casing 19 containing the vibrator 11, and possibly the processor 13,the cell or battery 12, and, as the case may be, one or more microphones14.

The external portion corresponding to the implantable portion 1 b shownin FIG. 9 is substantially identical to that shown in FIGS. 11 and 12,except that it includes only one magnetic part associated with thevibrator 11 that cooperates with the magnetic part 8 so as to cause theimplantable portion 1 b to vibrate.

FIGS. 13 to 16 show non-passive alternatives 1 c, 1 d of the implantableportion. In this alternative, the implantable portion is active and thusincludes a vibrator 11 coupled directly with a rod 2 c so as to transmitvibrations generated by the vibrator to the inner ear, preferably in theexternal semicircular canal. The vibrator 11 is associated withattachment means 32 enabling it to be attached to the skull and isconnected by electrical wires to an electronic processing casing 33,33′, which is itself connected by electrical wires to a circular antenna34, rigidly connected to one or two magnetic parts 35. In thealternative shown in FIG. 13, the electronic processing casing 33 isseparate from the circular antenna 34. The processing casing 33 can alsobe mounted directly on the vibrator 11. Similarly, the assembly of theantenna 34 and the magnetic parts 35 and the electronic casing 33′ canbe mounted on the vibrator 11. In this latter case, the rod 2 c ispreferably in the form of an elbow so as to prevent the risk of traumain the event of a shock.

In the alternative shown in FIG. 14, the electronic casing 33′ isencapsulated with the antenna 34. In the alternative shown in FIG. 15,the implantable portion 1 e comprises its own cell or battery powersupply 36. The antenna 34 makes it possible to ensure the transmissionof signals and/or power transmitted by an external casing. This externalcasing can include a signal-processing unit, a cell or battery andpossible one or more microphones 14. Indeed, in the devices that mustinclude at least one microphone, the latter can either be placed in theexternal casing or connected thereto, or be implanted.

In FIG. 16, the antenna portion 34 of the implantable portion 1 c, 1 d,1 e is attached to the skull away from the portion comprising thevibrator 11 and the rod 2 c. It should be noted that in theseembodiments, the rod 2 c does not need to be elbow-shaped because thevibrator 11 is also implanted, and, therefore, it is not necessary toprovide a plate 3 implanted just under the skin, capable of receivingshocks.

In FIGS. 17 and 18, the external portion 10 c corresponding to theinternal portion shown in FIG. 13, 14 or 15 includes a casing 19′containing a signal processor 13 connected to an antenna 21 and to apower supply 12, and possibly to a microphone 14. It also includes oneor two magnetic parts 18 corresponding to the magnetic parts 35 providedin the implantable portion so as to attach the external casing oppositethe antenna 34. If there are two magnetic parts, they are attached to asupport plate 20′ with the casing′.

FIGS. 19 to 24 show alternatives of the invention comprising a passive(percutaneous) semi-implantable portion.

In FIGS. 19 and 20, the implantable portion 1 f includes an elbow-shapedrod 2 f having an elbow angle and a length between the elbow and itsdistal end intended to come into direct contact with the inner ear,identical to that described in reference to FIGS. 1 and 2. The other endof the rod 2 is rigidly connected to attachment means 41 such as ascrew, intended to be attached to the patient's skull. The head of thescrew 41 includes an attachment profile 43 designed to cooperate with amatching profile provided on an external casing 50, 50′ shown in FIG. 21or 22. This casing contains a vibrator 11, and possibly a signalprocessor 13 connected to the vibrator, and, as the case may be, to atleast one microphone 14, as well as to a power supply 12 (FIG. 22). Inthe example shown in FIG. 21, the power supply 12 and the processor 13are arranged in another casing 55 connected by an electrical connectionto the casing 50.

The alternative of the invention shown in FIGS. 23 and 24 makes itpossible to treat patients who are entirely deaf in one ear. Near theentirely deaf ear, a screw 41 (FIG. 24) is attached to the skull, makingit possible to attach the casing 50′ containing in particular themicrophone, which enables vibrations to be generated, which aretransmitted in the skull by bone conduction. Near the other ear, animplantable portion 1 g, shown in FIG. 23, is attached, comprising a rod2 f as described above, rigidly connected not to a screw as shown inFIG. 19, but to means 45 for attaching the rod to the patient's skull,such as a disc provided for receiving a screw 46 intended to be screwedinto the skull, with the end of the rod 2 f being placed in contact withthe non-defective inner ear, as shown in FIG. 20. In this way, thesounds capable of being perceived by the defective ear are transmittedby the skull in the form of vibrations by bone conduction, then by meansof the rod 2 f directly into the non-defective inner ear.

1. Inner ear stimulation prosthesis including excitation means (11)designed to generate vibrations capable of exciting a patient's ear,characterized in that it comprises an implantable portion (1, 1 a to 1g), including a rod (2, 2 a, 2 c, 2 f) capable of transmittingvibrations and that is designed so as to be capable of transmittingvibrations generated by the excitation means (11) directly to thepatient's inner ear.
 2. Prosthesis according to claim 1, characterizedin that the rod (2, 2 a, 2 c, 2 f) is designed to be placed in contactwith a semicircular canal of the patient's inner ear.
 3. Prosthesisaccording to claim 1 or 2, characterized in that the rod (2, 2 a, 2 c, 2f) is designed to be placed in contact with the external semicircularcanal of the patient's inner ear.
 4. Prosthesis according to claim 1 or3, characterized in that the rod (2, 2 a, 2 c, 2 f) is made of a hardand rigid biocompatible material selected from metals, plastic materialsand ceramic materials.
 5. Prosthesis according to one of claims 1 to 4,characterized in that the rod (2, 2 a, 2 f) has a cross-section with aflattened shape.
 6. Prosthesis according to one of claims 1 to 5,characterized in that the rod (2, 2 a, 2 f) comprises at least one elbow(4) so as to be capable of connecting an external portion of thepatient's skull to the inner ear without requiring complex surgeryinvolving total anesthesia of the patient.
 7. Prosthesis according toclaim 6, characterized in that the rod (2, 2 a, 2 f) has a lengthbetween the elbow (4) and its end in contact with a portion of thepatient's inner ear, between 20 and 30 mm and has an elbow angle betweenits two end portions of between 70° and 130°.
 8. Prosthesis according toone of claims 1 to 7, characterized in that the surface of theimplantable portion (1) is treated so as to prevent anyosseointegration.
 9. Prosthesis according to one of claims 1 to 8,characterized in that the rod (2 a) is pivotably mounted on a support(7, 7′).
 10. Prosthesis according to one of claims 1 to 9, characterizedin that the excitation means (11) are arranged in an external casing(10, 10′, 10 a) and are designed so as to generate vibrations intendedto be transmitted through the patient's skin to a plate (3) rigidlyconnected to the rod (2, 2 a).
 11. Prosthesis according to claim 10,characterized in that the plate (3) has a substantially rectangularshape with foam edges of which the length is between 6 mm and 20 mm andthe width is between 3 mm and 10 mm.
 12. Prosthesis according to claim10 or 11, characterized in that the external casing (10, 10′, 10 a) isintegrated in an object capable of being held on the patient's head sothat the excitation means (11) are arranged opposite the plate (3) ofthe implantable portion (1).
 13. Prosthesis according to claim 12,characterized in that the object capable of being held on the patient'shead is selected from either a pair of eyeglasses or a casing that fitsaround the ear.
 14. Prosthesis according to one of claims 10 to 12,characterized in that the external casing (10 a) includes at least onemagnetic part (18) intended to cooperate with at least one magnetic part(8) provided in the implantable portion (1 a, 1 b) so as to hold theexcitation means opposite the plate (3).
 15. Prosthesis according to oneof claims 1 to 8, characterized in that the excitation means (11) areintegrated in the implantable portion (1 c, 1 d, 1 e) and coupleddirectly with the rod (2 c).
 16. Prosthesis according to one of claims 1to 8, characterized in that the rod (2 f) is rigidly connected toattachment means (41, 45, 46) for attaching the rod to the patient'sskull bone.
 17. Prosthesis according to claim 16, characterized in thatthe excitation means (11) are housed in an external casing (50, 50′)equipped with coupling means (51), so as to be removably attachedthrough the patient's skin to attachment means (41, 41′) intended to beattached to the patient's skull bone.
 18. Prosthesis according to claim17, characterized in that the external casing (50, 50′) containing amicrophone (14) is intended to be attached on the side of a totallydefective ear of the patient, while the rod (2 f) is intended to beattached so as to excite the other, non-defective, ear of the patient,with the vibrations generated by the excitation means being transmittedto the rod by bone conduction of the patient's skull bone.
 19. Hearingaid, characterized in that it is consistent with one of claims 1 to 18.20. Prosthesis for neurostimulation against tinnitus, characterized inthat it is consistent with one of claims 1 to
 19. 21. Prosthesis forneurostimulation against balance disorders, characterized in that it isconsistent with one of claims 1 to
 20. 22. Implantable prosthesisportion, characterized in that it is consistent with one of the previousclaims.